Doctor Answers (1) on Back pain, vomiting

Thank you for your query regarding the symptoms you have described. At the outset, when was your last menstrual period? If possibility exists please do a urine pregnancy test.

Could suggest a urinary tract infection as well so a urine for routine microscopy and culture will also be required.

Anything from renal calculi to an ovarian cyst may be the reason for your symptoms.
So you need to be evaluated by a local Gynaecologist for detailed history and examination. Till then drink plenty of water and take simple over- the- counter anti-emetics for symptom relief.